Статья

Multiple Exciton Generation in Colloidal Silicon Nanocrystals

Matthew C. BeardNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Kelly P. KnutsenNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Pingrong YuNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Joseph M. LutherNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Qing SongNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Wyatt K. MetzgerNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Randy J. EllingsonNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309Arthur J. NozikNational Renewable Energy Laboratory, Golden, Colorado 80401, Innovalight, Inc., Santa Clara, California 95054, Department of Applied Physics, Colorado School of Mines, Golden, Colorado 80401, and Department of Chemistry, University of Colorado, Boulder, Colorado 80309

2007en

ABI

Аннотация

Multiple exciton generation (MEG) is a process whereby multiple electron-hole pairs, or excitons, are produced upon absorption of a single photon in semiconductor nanocrystals (NCs) and represents a promising route to increased solar conversion efficiencies in single-junction photovoltaic cells. We report for the first time MEG yields in colloidal Si NCs using ultrafast transient absorption spectroscopy. We find the threshold photon energy for MEG in 9.5 nm diameter Si NCs (effective band gap identical with Eg = 1.20 eV) to be 2.4 +/- 0.1Eg and find an exciton-production quantum yield of 2.6 +/- 0.2 excitons per absorbed photon at 3.4Eg. While MEG has been previously reported in direct-gap semiconductor NCs of PbSe, PbS, PbTe, CdSe, and InAs, this represents the first report of MEG within indirect-gap semiconductor NCs. Furthermore, MEG is found in relatively large Si NCs (diameter equal to about twice the Bohr radius) such that the confinement energy is not large enough to produce a large blue-shift of the band gap (only 80 meV), but the Coulomb interaction is sufficiently enhanced to produce efficient MEG. Our findings are of particular importance because Si dominates the photovoltaic solar cell industry, presents no problems regarding abundance and accessibility within the Earth's crust, and poses no significant environmental problems regarding toxicity.

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Идентификаторы

DOI: 10.1021/nl071486l

Цитирования и источники

Цитирований: 4Использованных источников: 0

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